Field of the Invention
This invention relates to the transportation of objects, such as semiconductor wafers along a track on a film of air, and more particularly, to a manufacturing processing system and method in which a air track is used to transport objects to and from processing stations, including vacuum stations, at different elevations.
Previously, objects such as semiconductor wafers, which are subsequently divided into semiconductor chips, have been moved along a track on an air film during non-vacuum processing and testing of the semiconductor wafers. Mechanical robots have been used to pick the wafers off of the air track and dip them into, for example, a resist development solution. However, the most recently projected future semiconductor manufacturing processes employ techniques which permit very large scale integration (VLSI) of semiconductor chips or, in other words, a vast increase in the number of circuits per chip. Such techniques are E-beam lithography, dry or plasma etching, and ion implantation, all of which require a vacuum environment. In addition, semiconductors have been manufactured for a number of years using other vacuum techniques, such as vacuum deposition, sputtering, and sputter etching. The present trend is towards a "total vacuum" manufacturing process due to the demanding fabrication requirements and tighter tolerance controls to achieve reasonable yield levels of the VLSI devices. Yield levels are directly coupled to and critically dependent on stringent defect and contamination controls, which by definition must minimize or effectively eliminate human contact throughout the complete fabrication of the semiconductor wafer. The manufacturing process of high yield VLSI semiconductor chips must be a continuous wafer manufacturing system, preferably a "total vacuum" system to which an enclosed air film wafer transportation system is highly suited, such as described in U.S. Pat. No. 4,081,201 and 4,165,132, assigned to the same assignee. However, to be completely functional, such as air film transportation system must be such that mechanical robots are no longer necessary to change the elevation and angular orientation of the wafer because of potential damage to the wafer when it is gripped with the mechanical fingers of the robots. In other words, the air film transportation system must be able to perform these functions.